Carbon nitride (C3N4) thin films were grown on Si (100) substrates by microwave plasma enhanced chemical vapor deposition (PECVD). NH3 + CH4, 1H-1,2,3-triazole, hexamethylenetetramine (HMTA), and mixture of HMTA and 1H-1,2,3-triazole were used under N-2 flow as carbon and nitrogen sources. X-ray diffraction (XRD) analyses revealed that alpha- and beta-C3N4 phases were formed in the film deposited from HMTA. However, only graphitic carbon structures were observed when 1H-1,2,3-triazole was used as the precursor. Micromechanical properties of the deposited films were also investigated using a nanoindenter. Average microhardness and Young's modulus calculated for the films deposited from HMTA were found to be 35.0 +/- 9.0 and 686.0 +/- 181.0 GPa, respectively. This relatively high hardness value is indicative of the formation of a C3N4 phase. X-ray photoelectron spectroscopy (XPS) studies found that the ratio of sp(3)-bonded CN to sp(2)-bonded CN structures is the highest for the films deposited from HMTA among the sources tested. These evidences suggest that HMTA is a promising precursor to deposit C3N4 films by CVD. (C) 2004 Published by Elsevier B.V.